Among the flat panel display apparatuses, the active matrix organic light emitting diode (simply referred to as AMOLED) becomes an optimal choice of the display technique in the future due to advantages such as high image quality, short motion picture response time, low energy consumption, wide view angle, being ultralight and ultrathin, and the like. At present, in the technology of backplane of AMOLED, excimer laser annealing (simply referred to as ELA), solid phase crystallization, metal-induced crystallization, or the like is a mostly applied method for producing the polycrystalline silicon layer. The only method that has succeeded in industrial scale is to obtain the polycrystalline silicon thin film in the transistor active layer in the backplane by the excimer laser annealing process.
The excimer laser annealing process is a relatively complex annealing process. An ELA device is a device that irradiates an amorphous silicon film on a substrate with an excimer laser beam for a short time to produce a polycrystalline silicon film by the recrystallization of the amorphous silicon film. As shown in FIG. 1, which is a schematic diagram showing the construction of a laser annealing device in the prior art, the annealing device comprises a laser generator (not shown in FIG. 1), an annealing window 2, and two light-cutting plates 1 oppositely provided above the annealing window 2. One part of the laser beam emitted from the laser generator arrives at the amorphous silicon thin film 3 through the annealing window 2, while the other part is blocked and reflected back by the light-cutting plates 1. In the present specification, the end of the light-cutting plate, which reflects the laser beam, is referred to as the “light-cutting end”. As shown in FIG. 1, the ingoing beam 40 arrives at the amorphous silicon thin film 3 through the annealing window 2. The incident beam 41 arriving at the light-cutting plates 1 is reflected by the light-cutting plates 1, so that reflected beams 42 are formed. The travel direction of the ingoing beam 40 and that of the incident beam 41 are substantially the same. Since the included angle formed by the reflecting surface of the light-cutting plate 1 and the incident beam 41 is close to a right angle, the included angle a formed by the reflected beam 42 and the ingoing beam 40 is very small. Because the vibration direction of the reflected beam 42 and that of the ingoing beam 40 are similar, the phenomenon of interference will occur. This results in that there is interference mura on the produced polycrystalline silicon thin film. Such interference mura will affect the quality of the polycrystalline silicon. Meantime, in the manufacturing process, if interference mura on the polycrystalline silicon thin film occurs in succession, the percent of pass in the production process will finally decrease.
Therefore, the polycrystalline silicon thin film produced by the ELA device in the prior art can have interference mura, which results in the decrease of the percent of pass of the product.